Vue.component('app-footer', {
    template: "#app-footer",
    data() {
        return {
            ftMenu:['顺序', '逆序', '移动', '小于18'],
            selectedKey: -1
        }
    },
    methods: {
        select(key) {
            this.selectedKey = key;
            this.$emit('change', key);// 广播【broadcast】
        }
    }
});